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Skull Base. 2004 May; 14(2): 127–132.
PMCID: PMC1151682

Current Abstracts

TREATMENT OUTCOMES

Bruce E. Pollock, Paul C. Carpenter. Stereotactic radiosurgery as an alternative to fractionated radiotherapy for patients with recurrent or residual nonfunctioning pituitary adenomas. Neurosurgery 2003; 53: 1086–1094

Objective: To evaluate tumor control rates and complications after stereotactic radiosurgery for patients with nonfunctioning pituitary adenomas.

Methods: Between 1992 and 2000, 33 patients underwent radiosurgery for treatment of nonfunctioning pituitary adenomas. Thirty-two patients (97%) had undergone one or more previous tumor resections. Twenty-two patients (67%) had enlarging tumors before radiosurgery. The median tumor margin dose was 16 Gy (range, 12–20 Gy). The median follow-up period after radiosurgery was 43 months (range, 16–106 mo).

Results: Tumor size decreased for 16 patients, remained unchanged for 16 patients, and increased for 1 patient. The actuarial tumor growth control rates at 2 and 5 years after radiosurgery were 97%. No patient demonstrated any decline in visual function. Five of 18 patients (28%) with anterior pituitary function before radiosurgery developed new deficits, at a median of 24 months after radiosurgery. The actuarial risks of developing new anterior pituitary deficits were 18 and 41% at 2 and 5 years, respectively. No patient developed diabetes insipidus.

Conclusion: Stereotactic radiosurgery safely provides a high tumor control rate for patients with recurrent or residual nonfunctioning pituitary adenomas. However, despite encouraging early results, more long-term information is needed to determine whether radiosurgery is associated with lower risks of new endocrine deficits and radiation-induced neoplasms, compared with fractionated radiotherapy.

Daniel H. Kim, Yong-Jun Cho, Robert L. Tiel, David G. Kline. Surgical outcomes of 111 spinal accessory nerve injuries. Neurosurgery 2003;53:1106–1113

Objective: latrogenic injury to the spinal accessory nerve is not uncommon during neck surgery involving the posterior cervical triangle, because its superficial course here makes it susceptible. We review injury mechanisms, operative techniques, and surgical outcomes of 111 surgical repairs of the spinal accessory nerve.

Methods: This retrospective study examines clinical and surgical experience with spinal accessory nerve injuries at the Louisiana State University Health Sciences Center during a period of 23 years (1978–2000). Surgery was performed on the basis of anatomic and electrophysiological findings at the time of operation. Patients were followed up for an average of 25.6 months.

Results: The most frequent injury mechanism was iatrogenic (103 patients, 93%), and 82 (80%) of these injuries involved lymph node biopsies. Eight injuries were caused by stretch (five patients) and laceration (three patients). The most common procedures were graft repairs in 58 patients. End-to-end repair was used in 26 patients and neurolysis in 19 patients if the nerve was found in continuity with intraoperative electrical evidence of regeneration. Five neurotizations, two burials into muscle, and one removal of ligature material were also performed. More than 95% of patients treated by neurolysis supported by positive nerve action potential recordings improved to Grade 4 or higher. Of 84 patients with lesions repaired by graft or suture, 65 patients (77%) recovered to Grade 3 or higher. The average graft length was 1.5 inches.

Conclusion: Surgical exploration and repair of spinal accessory nerve injuries is difficult. With perseverance, however, these patients with complete or severe deficits achieved favorable functional outcomes through operative exploration and repair.

Douglas Kondziolka, Narendra Nathoo, John C. Flickinger, Ajay Niranjan, Ann H. Maitz, L. Dade Lunsford. Long-term results after radiosurgery for benign intracranial tumors. Neurosurgery 2003;53:815–822

Background: Stereotactic radiosurgery is the principal therapeutic alternative to resecting benign intracranial tumors. The goals of radiosurgery are the long-term prevention of tumor growth, the maintenance of patient function, and the prevention of new neurological deficits or adverse radiation effects. Evaluation of long-term outcomes more than 10 years after radiosurgery is needed.

Methods: We evaluated 285 consecutive patients who underwent radiosurgery for benign intracranial tumors between 1987 and 1992. Serial imaging studies were obtained, and clinical evaluations were performed. Our series included 157 patients with vestibular schwannomas, 85 patients with meningiomas, 28 patients with pituitary adenomas, 10 patients with other cranial nerve schwannomas, and 5 patients with craniopharyngiomas. Prior surgical resection had been performed in 44% of these patients, and prior radiotherapy had been administered in 5%. The median follow-up period was 10 years.

Results: Overall, 95% of the 285 patients in this series had imaging-defined local tumor control (63% had tumor regression, and 32% had no further tumor growth). The actuarial tumor control rate at 15 years was 93.7%. In 5% of the patients, delayed tumor growth was identified. Resection was performed after radiosurgery in 13 patients (5%). No patient developed a radiation-induced tumor. Eighty-one percent of the patients were still alive at the time of this analysis. Normal facial nerve function was maintained in 95% of patients who had normal function before undergoing treatment for acoustic neuromas.

Conclusion: Stereotactic radiosurgery provided high rates of tumor growth control, often with tumor regression, and low morbidity rates in patients with benign intracranial tumors when evaluated over the long term. This study supports radiosurgery as a reliable alternative to surgical resection for selected patients with benign intracranial tumors.

Vittorio Colletti, Francesco Fiorino. Middle fossa versus retrosigmoid-transmeatal approach in vestibular schwannoma surgery: a prospective study. Otol Neurotol 2003;24:927–934

Objective: To compare the advantages, disadvantages, and results obtained with the middle fossa and retrosigmoid-transmeatal approaches during pure intracanalar vestibular schwannoma surgery in an attempt to preserve hearing.

Study Design: Prospective study of patients treated from 1998 to 2001.

Setting: Tertiary care referral center.

Patients: Patients with intracanalar vestibular schwannoma (size ranging from 4 to 12 mm), 25 operated on with the retrosigmoid-transmeatal technique and 25 via the middle fossa route.

Main Outcome Measures: Facial nerve and auditory function were examined at 1 year with both techniques. Auditory results were also evaluated as a function of tumor size, distance from the internal auditory canal fundus, and internal auditory canal enlargement.

Results: The results indicated no significant difference in facial nerve and auditory function results between the two techniques. The retrosigmoid-transmeatal approach, however, yielded better facial nerve function results at discharge. Postoperative hearing was better when the distance from the fundus was greater than 3 mm, when the size of the vestibular schwannoma was equal to or less than 7 mm, and when the internal auditory canal enlargement was less than 3 mm.

Conclusions: The middle fossa approach does not afford any particular advantages over the retrosigmoid-transmeatal approach in terms of auditory results. Facial nerve function is less satisfactory in the short term, when the middle fossa route is used, but can be improved by decompression and gentle displacement of the facial nerve in its labyrinthine portion.

SURGICAL TECHNIQUES

Renato Donzelli, Gaetano Motta, Luigi Maria Cavallo, Francesco Maiuri, Enrico de Divitiis. One-stage removal of residual intracanalicular acoustic neuroma and hemihypoglossal-intratemporal facial nerve anastomosis: Technical note. Neurosurgery 2003;53:1444–1448

Objective and Importance: Incomplete removal of residual intracanalicular tumor and injury to the facial nerve are the main problems associated with surgery of large acoustic neuromas via the retromastoid suboccipital approach. In patients with residual or recurrent intracanalicular neuromas, the translabyrinthine approach is the preferred surgical route, allowing complete tumor removal; it may eventually also be used for exposure of the intratemporal portion of the facial nerve for a hemihypoglossal-facial nerve anastomosis when a postoperative facial palsy exists This one-stage procedure has not been described previously.

Clinical Presentation: Three patients with postoperative facial palsy and residual intracanalicular tumor after surgical removal of a large acoustic neuroma via the retromastoid suboccipital approach underwent reoperation via the translabyrinthine approach and one-stage removal of the residual tumor and hemihypoglossal-facial nerve anastomosis. All three patients had a complete facial palsy of House-Brackmann Grade VI and a residual tumor of 8 to 12 mm.

Technique: A classic translabyrinthine approach was used to open the internal auditory canal and remove the residual intracanalicular tumor. The facial nerve was exposed in its mastoid and tympanic parts, mobilized, and transected; then, the long nerve stump was transposed into the neck and used for an end-to-side anastomosis into the hypoglossal nerve. The operation resulted in variable improvement of the facial muscle function up to Grade III (one patient) and Grade IV (two patients).

Conclusion: Reoperation via the translabyrinthine approach is indicated for removal of residual intracanalicular acoustic neuroma and realization of a hypoglossal-facial nerve anastomosis in a single procedure. It is suggested that this type of anastomosis may also be used during the initial operation for acoustic neuroma removal when the facial nerve is inadvertently sectioned.

James K. Liu, David Decker, Steven D. Schaefer, Augustine L. Moscatello, Richard R. Orlandi, Martin H. Weiss, William T. Couldwell. Zones of approach for craniofacial resection: Minimizing facial incisions for resection of anterior cranial base and paranasal sinus tumors. Neurosurgery 2003;53:1126–1137

Objective: Anterior cranial base tumors are surgically resected with combined craniofacial approaches that frequently involve disfiguring facial incisions and facial osteotomies. The authors outline three operative zones of the anterior cranial base and paranasal sinuses in which tumors can be resected with three standard surgical approaches that minimize transfacial incisions and extensive facial osteotomies.

Methods: The zones were defined by performing dissections on 10 cadaveric heads and by evaluating radiographic images of patients with anterior cranial base tumors. The three approaches performed on each cadaver were transbasal, transmaxillary, and extended transsphenoidal.

Results: Three zones of approach were defined for accessing tumors of the anterior cranial base, nasal cavity, and paranasal sinuses. Zone 1 is exposed by the transbasal approach, which is limited anteriorly by the supraorbital rim, posteriorly by the optic chiasm and clivus, inferiorly by the palate, and laterally by the medial orbital walls. This approach allows access to the entire anterior cranial base, nasal cavity, and the majority of maxillary sinuses. The limitation imposed by the orbits results in a blind spot in the superolateral extent of the maxillary sinus. Zone 2 is exposed by a sublabial maxillotomy approach and accesses the entire maxillary sinus, including the superolateral blind spot and the ipsilateral anterior cavernous sinus. However, access to the anterior cranial base is limited. Zone 3 is exposed by the transsphenoidal approach. This approach accesses the midline structures but is limited by the lateral nasal walls and intracavernous carotid arteries.! An extended transsphenoidal approach allows further exposure to the anterior cranial base, clivus, or cavernous sinuses. The use of the endoscope facilitates tumor resection in the nasal cavity and paranasal sinuses.

Conclusion: The operative zones outlined offer minimally invasive craniofacial approaches to accessing lesions of the anterior cranial base and paranasal sinuses, obviating facial incisions and facial osteotomies. Case illustrations demonstrating the approach selection paradigm are presented.

Engin Gonul, Ersin Erdogan, Bulent Duz, Erdener Timurkaynak. Transmaxillary approach to the orbit: An anatomic study. Neurosurgery 2003;53:935–942

Objective: Various approaches to expose the orbit have been used, such as cranial, lateral, and medial approaches. In an effort to gain exposure to the orbit without necessitating a craniotomy, we have developed a transmaxillary approach to the orbit.

Methods: An approach was developed that uses data obtained by performing 24 orbit dissections in 12 cadaveric heads. After sublabial incision to expose the maxilla, maxillotomy is performed and the course of the infraorbital nerve is identified. The orbital floor is opened, and the orbit is accessed.

Results: This technique offers access to the inferomedial and inferolateral orbit and to the inferior aspect of the optic nerve.

Conclusion: The transmaxillary approach provides an entirely extradural approach to the orbit. This technique combines the benefits of a cosmetically acceptable approach with orbitotomy and avoids the use of craniotomy and brain retraction to access the deep medial, lateral, and inferior orbit. We advocate the transmaxillary approach to the orbit in cases of inferomedial posterior intraconal and inferolateral lesions as an alternative and adjunct to the standard techniques of orbital surgery.

Krzysztof Morawski, Fred F. Telischi, Faisal Merchant, Grzegorz Namyslowski, Grazyna Lisowska, Brenda L. Lonsbury-Martin. Preventing internal auditory artery vasospasm using topical papaverine: An animal study. Otol Neurotol 2003;24:918–926

Background: Internal auditory artery (IAA) spasm is thought to be one of the causes of postoperative sensory hearing loss after attempted hearing preservation removal of an acoustic neuroma. The use of topical papaverine, a nonspecific vasodilator, to prevent vascular insufficiency to the inner ear and to improve hearing outcomes has been suggested but not proven.

Materials and Methods: Vasospasm was mechanically induced by compressing the IAA in the control ears of six rabbits after application of topical saline. The subsequent reduction of cochlear blood flow (CBF) was measured using a laser-Doppler (LD) flow-monitoring technique. Functional loss of cochlear activity was verified with distortion product otoacoustic emissions (DPOAE). The contralateral experimental ears were treated with the topical application of papaverine directly to the IAA and cochleovestibular nerve complex. CBF and DPOAE were compared between the control and papaverine treated ears for 3-minute and 5-minute IAA compressions.

Results: Every control ear demonstrated some degree of postcompression IAA vasospasm (i.e., reduced CBF) and reduction of DPOAE. Nearly complete recovery of CBF and DPOAE to baseline was observed in all of the papaverine treated ears.

Conclusions: An animal model of IAA vasospasm was described. Mechanically induced vasospasm of the IAA was prevented by the topical application of papaverine. These findings have clinical implications for surgical procedures involving the internal auditory canal/cerebellopontine angle such as acoustic neuroma removal.

DIAGNOSIS

R. L. Humphriss, D. M. Baguley, D. A. Moffat. Head-shaking nystagmus in patients with a vestibular schwannoma. Clin Otolaryngol 2003;28:514–519

The aim of this study was to calculate the sensitivity of the head-shake test for peripheral and central vestibular dysfunction associated with unilateral sporadic vestibular schwannoma and to discuss the feasibility of using the head-shake test as a screening test. The study group consisted of 102 patients with unilateral sporadic vestibular schwannomas, who were seen consecutively for preoperative vestibular assessment, including the head-shake test. The sensitivity of the head-shake test for vestibular schwannoma was found to be 22%, and the sensitivity and specificity of the head-shake test for canal paresis (≥ 25%) were found to be 27% and 88%, respectively. Patients with abnormalities in the central vestibular system and with a greater canal paresis were more likely to have head-shake nystagmus, although, even for severe canal paresis, the sensitivity of the test remained low at 36%. The direction of nystagmus was found to be contra-lateral to the side of the tumour in 86% of patients. It was concluded that the head-shake test is of insufficient sensitivity to be used as a screening test either for vestibular schwannoma or for vestibular-system abnormalities associated with vestibular schwannoma. The deduction is made that the head-shake test is of insufficient sensitivity or specificity to be of clinical value as a screening test for vestibular dysfunction in a general population with symptoms of imbalance.

Nicolas Perez, Julio Rama-Lopez. Head-impulse and caloric tests in patients with dizziness. Otol Neurotol 2003;24:913–917

Objective: To test the performance of the head-impulse and caloric tests in terms of sensitivity, specificity, and predictive efficiency.

Study Design: This was an open and prospective study conducted at a tertiary care center in which 265 patients were subjected to the head-impulse test and caloric test on the same day. The results of the head-impulse test were considered as normal or pathologic. In a similar way, the caloric test was rated as normal when the difference in canal paresis was less than 22 percent and directional preponderance less than 28 percent, and abnormal if canal paresis was more than 22 percent and/or directional preponderance was more than 28 percent.

Main Outcome Measures: The results of each test were compared with obtain the specificity, sensitivity, and positive and negative predictive values. A receiver operating characteristics (ROC) curve was obtained from the false-alarm rate and the hit rate value of the head impulse test.

Results: The specificity of the head impulse test was 0.91 and the sensitivity was 0.45. The positive predictive value was 0.92, the negative predictive value was 0.41, and the area under the ROC curve was 0.866. A canal paresis value of 42.5 percent was considered to be the limit of the normal response, as seen when the head impulse test was used to predict a normal or abnormal result in a given patient.

Conclusion: The head impulse test, when used as a bedside test, and the caloric test are by no means redundant methods. The information obtained form both can be used in combination to obtain a better insight into the degree of vestibular dysfunction of patients.

DISEASE PROCESSES

Maurizio Falcioni, Alessandra Russo, Abdelkader Taibah, Mario Sanna. Facial nerve tumors. Otol Neurotol 2003;24:942–947

Objective: To evaluate the surgical results in primary facial nerve (FN) tumors.

Study Design: Retrospective case review.

Setting: Private neuro-otological and skull-base tertiary referral center.

Patients: Twenty eight consecutive patients affected by primary FN tumors that underwent surgery between December 1990 and February 2001.

Interventions: The lesions were removed through a variety of surgical approaches, depending on tumor location and extension, as well as preoperative hearing. In one case, partial removal was performed.

Main Outcome Measures: Preoperative and postoperative FN function; preoperative and postoperative hearing level; and postoperative complications.

Results: Based on histologic examination, tumors were distributed as follows: 18 schwannomas, six hemangiomas, two meningiomas, and two neurofibromas. Tumor location varied, with lesions distributed along the entire length of the nerve. Facial dysfunction was the most frequently recorded symptom, followed by hearing loss. Only five patients presented a preoperative grade 1 facial function. In the remaining patients of the group, the facial deficit lasted from 2 to 120 months, with a mean of 31.2 months. Anatomic integrity of the nerve was preserved in 4 cases; all others required a nerve interruption followed by reconstruction using a sural nerve graft. The complications recorded were: one cerebrospinal fluid leak, one postoperative retraction pocket, and one external auditory canal wall resorption requiring a surgical revision. Preoperative hearing remained unchanged in 8 out of the 15 patients in whom a hearing preservation procedure was attempted. In 25 cases, a follow-up of equal to or longer than 1 year was available, with the FN functions: two grade 1, eight grade 3, nine grade 4, three grade 5, and three grade 6. Patients with a preoperative deficit lasting more than 1 year demonstrated the worst recovery.

Conclusions: Primary FN tumors are rare lesions that include different histologic types. FN deficit represents the most common symptom, but it is not present in all cases. A conservative strategy is often adopted in presence of a normal preoperative facial function. When surgical management is selected, the decision on surgical approach to use depends on tumor size and location, as well as on preoperative hearing. FN integrity may be spared in rare occasions, but more frequently nerve reconstruction is required. Final facial function recovery is mainly dependent on the preoperative presence of FN deficit and its duration.


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